1. Field of the Invention
The present invention relates to a sunscreen composition having a particulate inorganic sunscreen stabilized and dispersed therein. The present invention further relates to a method for making a sunscreen composition in which a particulate inorganic sunscreen is stabilized and dispersed therein.
2. Description of the Related Art
Sunscreen compositions have commonly employed inorganic particulates, e.g., titanium dioxide and zinc oxide, in sunscreen agents. Such compositions have been formulated as anhydrous creams and lotions as well as aqueous emulsions. The most common form of emulsion employed is oil-in-water. Sunscreen emulsion compositions having inorganic sunscreen particulates are shown, for example, in U.S. Pat. Nos. 5,028,417; 5,188,831; 5,340,567; and 6,464,965.
One problem observed with sunscreen compositions having inorganic sunscreen particulates is they can feel heavy, oily, greasy and pasty in contact with the skin. Although oil-in-water emulsions exhibit these characteristics to a lesser degree than do water-in-oil emulsions or anhydrous creams and lotions, they nonetheless exhibit such characteristics.
Another problem observed with sunscreen compositions having inorganic sunscreen particulates is maintaining particulate dispersion and composition stability. One way employed in the prior art to improve dispersion and stability is to use particulates of very fine or relatively small sizes. Obtaining particulates of desired sizes may require use of complex grinding and/or milling processes.
Cosmetic compositions that employ organic and or inorganic pigments encounter many of the problems observed in sunscreen compositions. The term “pigment” refers to matter that imparts a phenomenon of light or visible perception that enables one to differentiate otherwise identical objects. Such pigments are typically supplied in particulate form like inorganic sunscreen particles. Compositions in which vibrant and rich color is desired require high levels of pigment, which can result in dispersion and agglomeration problems. Further, such compositions may not spread well. Pigment particulates are frequently treated or coated to reduce agglomeration and enhance dispersion and stability.
Carbomer gels have been employed in cosmetic and skin compositions because of their desirable aesthetic and feel properties. However, it has heretofore not been possible to use carbomer gels with a high loading of particulates due to dispersion and stability problems. The particulates have surface characteristics that can cause agglomeration and phase separation. Further, the gel breaks down and renders the composition nonfunctional as the pH of the gel changes over the course of time. Cosmetic and skin compositions having both a sunscreen and a carbomer are disclosed in U.S. Pat. Nos. 6,464,965; 6,491,930; and 6,521,217.
It would be desirable to have a composition having particulates that are stabilized and dispersed therein. It would also be desired to have such a composition in which the particulates are inorganic sunscreens and/or pigments. It would be further desired to have a composition with desirable aesthetic and feel characteristics on the skin. It would still be further desired to have a stabilized, dispersed carbomer gel composition having inorganic sunscreen and/or pigment particulates.